Problem: Subtract. $31 - 8.15 =$
Solution: There are many ways to solve this problem. Let's see two ways we can solve it. Place Value We can think in terms of hundredths: $\begin{aligned} &\phantom{=}31- 8.15\\\\ &=31.00-8.15\\\\ &=3{,}100\text{ hundredths} -815\text{ hundredths}\\\\ &=2{,}285\text{ hundredths}\\\\ &=22.85 \end{aligned}$ Place value table Let's line up the numbers by their decimal places. Tens Ones $.$ Tenths Hundredths ${3}$ ${1}$ $.$ ${0}$ $0$ $8$ $.$ ${1}$ $5$ Now, let's subtract each place value column. Tens Ones $.$ Tenths Hundredths $\overset{2}{\cancel{3}}$ $\overset{10}{\cancel{1}}$ $.$ $\overset{9}{\cancel{0}}$ $\overset{10}{\cancel{0}}$ $-$ $8$ $.$ ${1}$ $5$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $2$ $2$ $.$ $8$ $5$ $31 - 8.15=22.85$